This discussion discusses this topic Map marker identification
The complete discussion shows two ways to 'change the number' of a Marker. One uses CustomMarkers labeled 1,2,3,etc. (post 15), the other uses the Marker Info Box (post 4). Which labeling do you want to use?
The 'position changes'; then use the Marker.SetLocation latitude longitude Block to display a Marker at a new location. by providing the new latitude and longitude.
See Marker documentation
You might provide a more detailed explanation about what you want to do and tell us why you want to do this.